Hob grinding machine



Aug. 30, 1932. J. R. RICHER HOB GRINDING MACHINE Filgd June 28. 1930 4 Sheets-Sheet l Aug. 30, 1932. J. R. RICHER HOB GRINDING MACHINE Filed June 28. 1930 4 Sheets-Sheet 2 4 Sheets-Sheet 3 whw Q mm 9&

haw/Z07 kJFE'c/wm 1932- J. R. RICHER HOB GRINDING MACHINE Filed June 28. 1950 1932- J. R. RICHER HOB GRINDING MACHINE Filed June 28. 1930 Ell/671K 07 4 Sheets-Sheet 4 1 1 1 r 14 n V 4 2; A 1

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, Patented Aug. so, 1932 aosnrn a. stones, or

PATENT; OFFICE can rank, rumors nos GRINDING mncnmn v Application filed June 28,

My invention relates to grinding machines and particularly to machines for grinding hob teeth.

Heretofore it has been a common practice to use a conical grinding wheel for grinding" the sides of hob teeth. This wheel has been mountedon a spindle which in turn is carried by a holder, and the holder has been shiftable so as to enable the conical wheel to be shifted m in accordance with the angle of the thread in the hob. @ne of the difiiculties which has been presented in connection with the conventional machines, resides in the factthat when the grinding wheel is shifted for the purpose 5 or" accommodating said wheel to the thread angle, the pointof contact of the wheel with y the work is shifted, thereby inducing certain errors which must be compensated for. l

' t is one of the primary obj ects of the pres go out invention to provide a machine for grinding hobs and the like, in which the line of contact of the grinder with the work will not be shifted when the spindle of the grinder is tilted for the purpose of adjustin the grinder to conform to the angle of the t ead in a hob.

Another object is to provide a grindin machine, in which a theoretical, correct axis is provided, about which a grinder head may be tilted in accordance with the helix angle of the thread in a hob for the purpose set forth above. V

More specifically, it is an object of my in vention to provide a grinding machine with a tiltable grinder holder, the axis of said grinder holder when extended being substantially coincident with the line contact of the grinder with the work. F Still another object is to provide simple and improved means, whereby the recipro eating stroke of a grindermay be varied While the grinding machine is in operation.

A further object is to provide in a machine for grinding hob teeth and the like having a rotary cam for .efiecting the reciprocation of a grinder, means for preventing rotationlof the cam as a result of spring pressure acting agaihst an inclined surface thereon:

A still further object is to provide a Inachine as set forth above having improved 1930. Serial No. 464,461.

means for causiiig the grinding wheel to operate upon the hob teeth as said wheel is being played away from the axis of the supported Numerous other objects and advantages @5 will be apparent from the following detailed. description when considered in connection with the accompanying drawings, wherein- Figure 1 is a front elevational view of a grindmg machine which is representative or 6% 7 one embodiment of my invention;

Figure 2 is an enlarged vertical sectional view of the machine taken substantially along the line 2-2 of Figure 1; a

Figure 3 is a longitudinal vertical sectional' view taken substantially along the line 33 of Figure 2;

Figure 4 is an enlarged plan view of the grinder head and work support shown in Figure 1, certain portions of the well as the supported hob, being shown 1n section for the purpose of more clearly illustrating my invention; 4

Figure 5 is a detail vertical sectional view taken substantially along the line 5-5 of n; Figure 4;

Figure 6 is a plan view similar to Figure 4, disclosing the grinder shifted to a position for grinding the opposite sides of the hob teeth;

Figure 7 is an enlarged sectional view taken along the line 88 of Figure 4 to more clearly show the relation between the grinder, the axis about which it is tiltable, and the axis of the work spindle; and

Figure 8 is a vertical transverse sectional view of the work spindle and lead screw, said view being taken substantially along the line 88 of Figure 3. I

Referring now to the drawings more in on detail, wherein like numerals have been employed to designate similar parts throughout the various figures, it will be observed that one embodiment of my invention resides in a hob grinding machine which includes a frame 10, which is supported by a suitable base 12. lhe upper portion ofthe frame 10 presents a housing 14: which encloses a work suppbrting spindle 16. This spindle 16 is provided with a reduced work rec grinder, as m supporting end 18 which is adapted to receive and rotate a hob 20. A hearing 22 provides one support for the spindle, while the opposite extremity of the spindle passes through a hollow lead screw 24. This lead screw 24 is supported by and is rotatable within a companion split nut 26 which is secured against rotation within an annular supporting member 28, later to be described. Rotation is imparted to the spindle 16 through 'the agency of a large gear 30 mounted thereon which meshes with an elongated pinion 32, Figure 3. This pinion 32 is driven from a motor 34 shown in Figure 1. A clutch mechanism 36 is controlled by a manually shiftable lever 38. This clutch 36 may be of any conventional design and when the lever 36 occupies the central position shown in Figure 1, power will not be delivered to the elongated pinion 32. By shifting the lever to one side, rotation will be imparted in a given direction to the pinion, and a reverse direction of rotation will be occasioned when the lever is shifted to the opposite side.

The hollow lead screw 24 may be directly coupled with the spindle 16 means of a radial arm 40, Figure 3, which is clamped in position upon the outer end of the lead screw and a second arm 42 pivotally carried upon the arm 40 which is adapted to interlock with a gear 44 mounted upon the left extremity of the work spindle. When the pivotedarm 42 is swung downwardly to the position shown in Figure 3 and is interlocked with the teeth of the gear 44, a direct driving connection is established between the hollow lead screw 24 and the work spindle. WVhen it is desired to longitudinally adjust the position of the spindle without disturbing the position of any of the other parts of the machine such as the position of the grinder head 46, later to be described, the arm 42 may be swung out of engagement with the teeth in the gear 44. It will be noted that the hollow lead screw is supported at one extremity upon a tapered bearing sur-' face 48 of the spindle and at its opposite extremity upon the tapered bearing surface of a, collar 50 which is continually urged against the companion tapered surface of the lead screw by means of a coiled spring 52 which is interposed between the collar 50 andthe' gear 44. In this manner the lead 55 screw is supported at both extremities and when the driving connection between the lead screw and the spindle is interrupted as by he imparted raising the arm 42, rotation may to said lead screw by manually turning a hand wheel 54. v 1 Referring now to the grinder head 46 referred to above and particularly to Figures 2, 4, 6, and 7, it will be seen that this grinder head includes a holder 56 for supporting a cylindrical housing 58. This housing 58 in specific construction of the spindle and its cylindrical support is clearly shown in Figure 4. This grinder spindle 60 is driven at high speed by a motor 64 which is coupled therewith through the agency of a suitable belt 66 and pulley 68. Screws 70 in the holder 56, when tightened, firmly clamp the cylindrical housing 58 in position. This holder 56 is provided with an integral base section 72, Figures 4 to 6 inclusive, which is provided with an aperture 7 4 for receiving a vertically disposed securing bolt 76. The base section 72 is provided with a central portion having opposed cylindrical surfaces, the lower surface resting against a companion cylindrical surface provided in a .support 78, and the upper cylindrical surface adapted to receive a clamping plate 80. This plate 80 is clamped against the cylindrical surface of the section 72 by means of the bolt 7 6.

If a line coincident with the line of contact at the point of tangency of the grinding wheel 62 and the tooth of the hob 20 is extended, this line will pass through the center of the bolt 76 as clearly shown in Figure 4 wherein said line is designated by the dot and dash line 84. This line 84 crosses the axis of the bolt 76 at a point included within the axis about which the base section v is adjustably rotatable. This point is designated by the letter A in Figure 5. In other words, the grinder head 46 is adjustable about an axis which if extended, is coinciwhich is parallel to and in fact coincident l with the line of contactmade between the conical surface of the grinder and the side of the hob tooth.

By having the grinder adjustable about I the above mentioned axis, it will be seen that regardless of the position to which the grinder spindle is shifted for the purpose of adjusting the grinder to a particular thread, no variation in the line contact by the grinder wheel will be occasioned. This is to be clearly distinguished from devices which have been used heretofore wherein a grinder headis shifted about an axis which is so positioned as to introduce variation in the vertical disposition of the line contact made by the grinder wheel when adjustmehts for Figure 7 I have designated the the machine frame 10.

thread. angle are made. It will also be noticed that this axis which is designated by.

the line 84, Figure 4, lies in a horizontal plane and intersects the axis of the work supporting spindle 16. Furthermore, this axis or line 84 is positioned obliquely with respect to the axis of the work spindle. L In axis of the work spindle bv a dotand dash line 86, the axis of the grinder wheel by a dot and dash line 88, and a third dot anddash line diagrammatically designates the side surface of the hob teeth or in other words, the thread angle. From the foregoingdescription it will be apparent that the center line of adjustment of the grinder or. mother words, the axis of tilting thereof is paral el to the grinding zone of the grinder wheel and is contained thereip so that when the grinder head is tilted about this line, the contact line within said grinding zone is not disturbed vertically at any part thereof. I The support 78 for the grinder head 46 is mounted upon a suitable plate 91 which is in turn mounted on aslide 92 and is secured to said slide by means of bolts 94 and 96, Figure 2. This slide 92-is adjustable in parallelism with the axis 86 of the work spindle 16 upon a guide frame 98 through the agency of a su table control handle 100. Figure 1.

lhis guide frame 98 extends i'sransverselvv of the machine and is mounted upon suitable anti-friction or ball bearing supports 102 and is transversely shiitable on said support. A coiled spring 104 serves to continually urge guide frame or slide to the left, Figure 2, the upper extremities of said spring being secured to the rear end of the guide frame and the lower end secured in a fixed position upon it will thus be apparent that the guide frame 98 is reciprocable transversely of the machine for the purpose ofproperly presenting the grinder wheel to the relieved surfaces of the hob teeth. 'lrans verse movement or the slide 98 is controlled by means of a cam 108 which is mounted upon a shaft 108, Figures 2 and 3. This cam rotates in the direction indicated by the arrow in Figure 2 and engages the lower end of an actuating linger 110, which finger is pivotally connected at its upper extremity to the underside of an adjustable member or frame 112. lhe left surface of the linger 110; as viewed in igure 2. iulcrums upon the. adjacent edge of a t -shaped projection 11a wh ch is carried by an adjusting screw 116. A depending lug 118 at the lower end of a bolt 120 provides the pivotal support for the linger 110 and the frame 112 which carries the depending lug 118 is adjustable transversely of the machine by means er a suitable handle 122 carried at "he outer extremity of a screw 12%., Figure 2. in "other words, horizontal adjustment of the pivotal point of the linger 110 with respect to the guide frame 98 may be made by manually manipulating the handle 122. Vertical adjustment of the fulcrum or projection 114 may be made by imparting rotation to the screw 116 and this is occasioned by applying a wrench or similar device to the outer square end of a stub shaft '126 which is connected by bevel gears 128 and 130 to-the, screw 116. A tightening or lock nut 132 serves to lock the projection or fulcrum 118 in its various positions of vertical adjustment. It will be apparent that the vertical adjustment of the fulcrum may be made without interrupting the operationof the cam 106.

It will be observed that as the cam 108 moves from the position shown in Figure 2, the finger 110 will be gradually swung in a clockwise direction about-the fulcrum 11 1, thereby imparting a gradual rearward movement to the grinder wheel 62. The cam is so constructed that the shifting of the grinder wheel will be in accordance with the relief in the hob teeth. In this. connection .it should be observed that it is the usual prac tice to feed a grinding wheel toward the work in grinding the relieved surfaces of hob teeth and that my invention contemplates the application of the tool or grinder wheel in a reverse direction, namely in a direction away from the work. When the cam 106 has been rotated so as to face 106a: into engagement with the finger 110, a sudden movement toward the work will be experienced by the grinder wheel so as to carry said wheel into position to grind the neat succeeding'hob toot Rotation is imoarted to the cam shaft 108 by means of a clutch mechanism which I have designated generally by the numeral 135-, Fig: ure 8. This mechanism includes a clutch member 186 which is secured to the cam Shah; 1178 and a mber 188 which is resiliently connected to a crive shaft through the agency of a coiled spring 142. This shaft 140 is driven through a train of gears connected the elongat d pinion 32. Gertainoi these gearsare designated in 1 by the numerals 1 1 1 and 146. Springs positioned on opposite sides of the guide frame 98 serve to hold said frame against its ball bearing suppor larticular a ner in which 1 have constructed the jaws of the clutch members 136 and 188. It will be apparent that when the clutch members are operatively engaged and the shafts 1 10 and 108 are rotating in a counter-clockwise direction as viewed Figures 2 and 3, there will be a positive yielding driving force imparted to the cam shaft 108. llo\\'ever,, when the elongated pinion 82 is rotated in a reverse direction for the purpose of shifting the work spindle in a reverse direction, the inclination of the clutch is such as. to enable. the

bring the fiat side sur- "ention is directed to the man-- timing of the grinding wheel.

in a direction opposite to When the highest surface portion of the cam 106, namely the surface portion designated by the numeral 106b, engages the finger 110, the grinder wheel 62 will be positioned out of engagement with the hob teeth so as to clear the tops words, the cam is so designed that when the grinding action of the wheel is completed, said wheel is moved so as to clear the tops of the hob teeth. It will thus be apparent that when a grinding operation from one extremity of the .hob tooth to the other has been completed, it is desirable to have the grinding wheel positioned out of engagement with the work in order to facilitate the rearward shifting of the work spindle. In order to insure the positioning of the grinderwheel out of engagement with the work when the machine is thrown in reverse, I employ a pawl 147, Figures 2 and 3, which is adapted to en-' gage a tooth 149 of a ratchet 151 which is rotatable with the cam shaft 108. It will be seen from these figures that when the cam shaft is reversed, that is, when it is rotated that indicated in Figure 2, the tooth 149 of the ratchet will engage the pawl 147 when the surface portion 106?) of the cam engages the actuating finger 110. After the cam 106 is thus secured against reverse rotation by said pawl and ratchet mechanism, the clutchmembei' 138 will clickpast the clutch member 136. In this manner the grinder wheel will be automatically positioned out of engagement with the work the instant that the machine is thrown into reverse. This eliminates the usual manual manipulation of the grinder wheel slide by the operator in order to move the grinder wheel away from the work piece.

, When he grinding machinefis thrown into forward or operating movement, the pawl 151 and the j grinder will perform its usual relieving opthat I provide engaging eration.

Attention is further directed to the fact surfaces at the point designated by the letter B in Figure 3 which are such as to prevent the earn 106 from being.

rotated ahead of it's normal position when thefinger 110 engages the flat surface 106a during theforward rotation of the cam as indicated by the arrow in Figure2. In other words, the action of the springs 104 upon the finger 110 would be engages the cam surface cam 106 to rotate in a such, when said finger 1060, as to cause the direction indicated by the arrow in Figure 2 if sufiicient resist ance were not offered by the engaging surfaces at-the point B, Figure 3. It might be stated that the clutch members 136 and 138 are] locked in both directions while in driving position, but are impositively locked when of said teeth. In other member 134 when the grinding machine is thrown in reverse and the ratchet tooth 149 engages the pawl. 147. v

Attention is now directed to the specific -manner in which I mount the hollow lead screw 24 in the split nut 26, see Figures 3 and 8. The nut 26 is provided with oppositely disposed radial lugs 148 and these lugs 148 project upwardly into companion apertures provided within the annular housing 28. This housing 28 which are secured together by means of suitable screws 150. Springs urge the split sections of the nut 26 toward the threads in the lead screw, thereby taking up all back-lash or wear. The housing members 28 are pivotally supported and secured withina bearing 154 by means of suitable pins-156. From the that the hollow lead screw is in reality rotatable within'a universally supported nut. This will be apparent when it is seen that the lugs 148 provide an axis in one'direction for said nut while the pins 156 provide a second axis at right angles to the axis of said lugs. This arrangement provides a very practical and serviceable supporting arrangement. Any variations experienced .by the lead screw will be taken up in such a universal support, thereby enabling said lead screw to be subjected to severe usage over 152 resiliently is provided in two sections foregoing it will be seen an extended period of time without the necessity of replacement.

In Figure which the grinder head may be positioned to grind the side of the hob teeth opposite to that shown in Figure 4. This is accomplished by shifting the bolt 76 to an aperture 158, Figure 5, provided in the plate In this new posltion the base section 72 is inverted and secured in position as shown in 6 I have shown the manner in Figure 6. The dot and dash line 84a. shown I I have disclosed a truing se does not form the subject matter of my present invention but is merely shown in combination with the grinder head 46. This truingmechanism includes a block or frame 162 which is dovetailed to one extremity of the base section 72 as clearly shown in Fign which, if extended, is coincident with and ure 7. A finger1164 is positioned adjacent the conicaL side of the grinding wheel and is adapted to be moved across the surface thereof for the purpose of truing said wheel. From the foregoing description it will be apparent that my lnvention contemplates the provision of improved means and-methods whereby the sides of a hob tooth may be ground Bytilting the grinder about an axis parallel to the line contact between the grinder and the work, errors which have heretofore been introduced as a result of the shifting of this line contact, are avoided.

My improved apparatus is'of simple design and maybe manufactured by the practice of usual machine shop methods. Shifting the grinder wheel away from the axis of the work piece in the manner set forth above, go has proven very satisfactory and my improved means for shifting the position of the fulcrum which bears against the actuating finger enables adjustments to be made while the machine is in operation. The improved click clutch arrangement in combination with the type of cam surface shown in the drawings, precludes the possibility of rotating the cam ahead of its timed position. By practicing my improved method, hobs so maybe ground in a very expeditious and "economical manner.

It will also be apparent that my grinder may be moved toward the work piece during the grinding operation instead of away from the work, as above described, by merely positioning the contact lever or finger 110 on the opposite side of the cam By positioning the parts in this manner the grinder will be moved slightly toward the worlr and rapidly away from the worlr.

Changes in the specific arrangement of the structure shown in the drawings may be made without departing from the spirit and scope of my invention, and said invention should be limited only by the scope of the teeth.

the axis about which said holder is tiltable it lln a hob grinding machine, a rotatable work support, a grinder spindle, a grinder on said spindle, a holder for said spindle, ,rneans tor tiltably supporting said holder,

extended, being substantially ciiincident with the line of contact of the grinder with the work and inclined with respect to and intersecting the axis of the rotatable work support, and means for imparting relative move ment between the grinder and the work in accordance with the relief on the hob teeth.

3. In a hob grinding machine, a rotatable work support, a'grinder spindle, a conical grinder on said spindle, aholder for said spindle, means for tiltably supporting said holder, the axis about which said holder is tiltable, if projected, being substantially coincident with'the line of contact of the conical surface of the grinder with the work whereby to enable the shifting of said grinder in accordance with the thread angle of the hob without disturbing the line contact of the grinder with the work, and-means for imparting relative movement between the grinder and-the work in accordance with the relief on the hob teeth.

d. In a hob grinding machine, a rotatable work support, a grinder spindle, a grinder on said spindle, a holder for said spindle, means for tiltably supporting said holder,

said holder being tiltable about an axis positioned obliquely with respect to the axis of the rotatable work support and shiitable about an axis at substantially right angles with respect to the axis of said rotatable work support, and means for imparting relative movement between the grinder and the work in accordance with the relief on the hob teeth. Y W

5. In a hob grinding machine, a rotatable work support, a grinder spindle having, its axis of rotation substantially normal to the hob helix, a grinder on said spindle, a holder for said spindle, means for tiltably supporting said holder, the axis about which said holder is tiltable, it projected, being substantially coincident with the line of contact the grinder with the work, and impartin relative movement between the grinder and "the work in accordance with the reliei on the hob teeth.

6. In a hob grinding machine, a rotatable work support, a grinder spindle, a grinder on said spindle, a holder for said spindle, and

means for tilt-ably supporting said holder,

said holder being tiltable about a substantially horizontal axis which is oblique with respect to the axis of the work support for adjusting said grinder to the thread angle of the hob and shiftable about a substantially vertical axis for adjusting to the pressure angle of hob.

7. In a hob grinding machine, a rotatable work support, a grinder spindle, a grinder on said spindle, a holder for said spindle, means for tiltably supporting said holder, and means for imparting relative reciprocation between the grinder and supported work,

said, holder being tiltable about an axis llld i work support, a grinder oblique to the axis of the Work support for adjusting said grinder to the thread angle of the hob and shiftable about an axis, substantially normal to the plane of reciprocation for adjusting said grinder to the pressure angle of the hob.

er and the work in accordance with the relief in the hob teeth, a lead screw for imparting longitudinal movement to said work support, a nut in which the lead screw is movable, and means for supporting said nut about a pair of axes disposed at substantially right angles to each other, whereby to present a universal support for said nut.

10. In a hob grinding machine, a rotatable work support, a grinder, means for imparting relative reciprocation between the grinder and thework in accordance with the relief in the hob teeth, a lead screw for imparting longitudinal movement to said work support,

a nut in which the lead screw is movable,

an annular means providing a pivotal support for said nut, and a bearing providing a pivotal support for said annular means.

11. In a hob grinding machine, a rotatable work support, a grinder, means for imparting relative reciprocation between the grinder and the work in accordance with the relief in the hob teeth, a lead screw for imparting longitudinal movement to said work support, a split nut in which the lead screw is movable means for supporting said split nut about a pair of axes so as to present a uni versal support, and resilient means for continuously urging the split portions of the nut against the lead screw.

12. In a machine of the class described, a

rotatable support, means for imparting lonitudinal movement to said support includmg a lead screw, a split nut for said lead screw, resilient means for continuously urgmg said nuttoward said lead screw, means for supporting said nut about a transverse axis, and means for supporting said nut support about an axis disposed at substantially right .angles to said first mentioned axis whereby to present a universal support for .said nut.

13. In a machine of the class described, a rotatable work support, a tool for engaging work on said support, a lead screw forimpart 'work on said support, a lead screw ing longitudinal movement to said work support, driving means for rotatingsaid lead screw, a cam mechanism for imparting relative reciprocation between the tool and work support, said mechanism including acamhaving a gradually rising surface and a relative- 1y steep surface, and a clutch mechanism for connecting the driving means with said cam,

'said clutch mechanism including a pair of clutch jaws adapted to positively connect theparts in one direction of rotation and to impositively connect the parts in the opposite direction of rotation, and an actuating member engaging the cam surface, the impositive frictional engagement of the clutch jaws being greater than the frictional engagement of said actuating member with the steep surface of said cam.

14:. In a machine of the class described, a rotatable work support, a tool for engaging work on said support, a lead screw for imparting longitudinal movement to said work support, driving means for rotating said lead screw, a cam mechanism for imparting relative reciprocation between the tool and work support, said mechanism including a camhaving a gradually rising surface and a relatively steep surface, and a clutch mechanism for connecting the driving means with said cam, sald clutch mechanism including a pair of clutch jaws adapted to positively connect the parts in one direction of rotation and to impositively connect the parts in the opposite direction of rotation, an actuating member engaging the surfaceof said cam, and a pawl and ratchet mechanism for preventing reverse rotation of said cam and for stopping the cam when the highest surface thereof engages the actuating member,

15. In a machine of the class described, a rotatable work support, a'tool for engaging work on said support, a lead screw for im parting longitudinal movement to said work support, driving means for rotating said lead screw, a cam mechanism for imparting relative reciprocation between the tool and work support, said mechanism including acamhavfulcrum about which 'said actuating member operates, and means for shifting the position of said fixed fulcrum'to vary the degree of movement of said actuating member.

' 16. In a machine of the class described, a

rotatable work support, a tool for enfgaging parting longitudinal movement to said work support, driving means for rotating said lead screw, a cam mechanism for imparting relative reciprocation between the tool and work support, said mechanism inclu'dingacamhaving a gradually rising surface and a relatively steep surface, and a clutch mechanism for connecting the driving means with said cam,

said clutch mechanism including a pair of clutch jaws adapted to positively connect the parts in one direction of rotation and to impositively connect the parts in the opposite direction of rotation, an actuating member engaging the surface of said cam, a tool supporting slide pivoted to said actuating memher, a fulcrum interposed between said pivotal point and the point of engagement of the member with the cam, and means for adj usting the position of said fulcrum.

17 In a hob grinding machine, a rotatable work support, a grinder spindle, a grinder carried by said spindle, a holder for said spindle, a cylindrical bearing for tiltably supporting said holder, and a pivotal device extending through and at substantially right angles to the cylindrical bearing whereby to effect the adjustment of the grinder wheel to the pressure angle of the hob to be ground.

18. In a hob grinding machine, a rotatable work support, a grinder spindle, a grinder carried by said spindle, a holder for said spindle, a cylindrical bearing for tiltably supporting said holder, and a clamping mechanism including a clamping screw extending at substantially right angles to and through the cylindrical holder support whereby to effect the adjustment of the grinder in accordance with the required pressure angle of the hob to be ground and to secure said holder in such position.

19. In a hob grinding machine, a rotatable hob support, a grinder spindle, a grinder carried by said spindle, a holder for supporting said spindle at either side of a vertical plane that is perpendicular to the hob axis with the spindle substantially perpendicular to the hob helix and oblique to the hob axis,'said holder providing a pivotal support to render said spindle adjustable to the thread angle of the hob, the axis of said pivotal support being substantially parallel with the grinding surface of said grinder, means for producing relative travel between the grinder and the hob in a direction parallel to the hob axis, and means for efi'ecting relative transverse movement between the grinder and'the hob for grinding the relief on the teeth of the hob.

being substantially parallel with the grinding surface of said grinder, a second pivotal 7 means for rendering the spindle adjustable to the pressure angle of the hob teeth, means for producing relative travel between the grinder and the hob in a direction parallel to the hob axis, and means for eflecting relative transverse movement between the grinder and the hob for grinding the relief on the teeth of the hob.

21. In a hob grinding machine, a rotatable hob support, a grinder spindle, a grinder carried by said spindle, supporting means for positioning the axis of the grinder spindle substantially perpendicular to the thread helix of the hob and providing a pivotal support f9r rendering the grinder adjustable to the thread angle of the hob, the axis of said pivotal support being oblique with respect to the'axis of the rotatable hob support and substantially parallel with the grinding surface of said grinder, means for effecting relative movement between the grinder and hob support in a direction substantially parallel to the hob support axis, and means for effecting relative transverse movement between the hob support and grinder in accordance with the required relief on the hob teeth.

22. In a hob grinding machine, a rotatable work support, a grinder spindle, a grinder on said spindle, a holder for said spindle, means for tiltably supporting said holder, the axis about which said holder is tiltable, if projected, being substantially parallel with the holder, the axis about which said holder is tiltable, if projected, being substantially parallel with the conical surface of the grindder, and means for imparting relative movement between the grinder and the work in accordance with the relief on the hob teeth.

In witness whereof, I have hereunto subscribed my name.

JOSEPH R. RIOHER. 

